Evaluating the Uncertainty in the Temperature Reactivity Coefficient of Terrestrial Energy's Integral Molten Salt Reactor Design

位于安大略省奥克维尔的陆基能源公司最近获得了加拿大可持续发展技术公司的一项重要奖项，允许其继续开发其有前途的新型核反应堆设计，即整体熔盐反应堆（IMSR）。从成本、规模、可维护性和安全性的角度来看，该反应堆具有许多特点，使其在当前的全球电力市场中处于领先地位。这种反应堆设计的突出特点之一是其固有的安全性。由于核燃料溶解在熔盐中，所以不可能发生堆芯熔毁。此外，根据设计，反应器具有负的温度反应性系数。这意味着当堆芯温度上升时，一个固有的反馈机制将关闭堆芯中的连锁反应，就像在假设的事故条件下可能发生的那样。温度的反应性系数是发生在核心的核物理过程的结果，它控制着链式反应中中子的产生和吸收。由于竞争效应的差异，这是一个相对较小的效应，对于IMSR来说，确定在反应堆的寿命期间为负。这里提出的研究将确定IMSR的反应性温度系数值的不确定性，这对于建立反应堆在其生命周期内运行的安全裕度至关重要。该研究将使用国际上为核安全分析开发的最先进的建模工具。除了计算拟议的燃料组成外，这项研究还将应用于若干替代燃料组成。这里提出的研究是证明设计固有安全特性的重要贡献。

Terrestrial Energy of Oakville, Ontario has recently received a major award from Sustainable DevelopmentTechnology Canada, allowing it to proceed with the development of its promising novel nuclear reactor design,the Integral Molten Salt Reactor (IMSR). This reactor has a number of features which places it well in thecurrent global electricity market, from the perspectives of cost, size, maintainability and safety.One of the outstanding features of this reactor design is its inherent safety. As the nuclear fuel is dissolved inmolten salts, there is no possibility for a core meltdown. Also, by design, the reactor has a negative reactivitycoefficient of temperature. This means that an inherent feedback mechanism will shut down the chain reactionin the core when the temperature of the core rises, as may happen under hypothetical accident conditions.The reactivity coefficient of temperature is a consequence of the nuclear-physics processes that take place inthe core and govern the creation and absorption of neutrons in the chain reaction. It is a relatively small effectarising from the difference of competing effects, which for the IMSR was determined to be negative over thelifetime of the reactor.The study proposed here will determine the uncertainty in the value of the reactivity coefficient of temperaturefor the IMSR, which is essential to establish the margin of safety for reactor operation over its lifetime. Thestudy will use state-of-the-art modelling tools developed internationally for nuclear safety analysis. In additionto calculations for the proposed fuel composition, the study will also be applied to a number of alternate fuelcompositions.The study proposed here is an essential contribution to demonstrating the inherent safety features of the design.